We contributed to NTP technical reports of rodent bioassays on aloe vera, Ginkgo biloba, pyrogallol, trimethylolpropane triacrylate, n,n-dimethyl-p-toluidine and beta-picoline that were reviewed and accepted by the NTP Board of Scientific Counselors. We also participated in study design committees for over 12 chemicals that will be tested by the NTP. We published papers in the scientific literature on chemicals that were recently tested by the NTP: Panax ginseng, goldenseal root powder, milk thistle extract, 1-bromopropane, and hexavalent chromium. The NTP's extensive testing program provides opportunities to investigate patterns across studies. We contributed to a multi-study evaluation of rat pancreatic islet cell tumors which showed that protein expression in these tumors was similar to that found in humans. The immunohistochemical characterization of these tumors also provided indications of possible pathways for carcinogenesis in islet cells. We also contributed to a study of whether chemically-induced kidney tumors in rats can be predicted from histological kidney changes observed in short-term studies. We found that the occurrence of dose-related chronic progressive nephropathy in a 90-day study of a chemical is an excellent predictor that the chemical will produce renal tubule tumors in 2-year studies. We continued to provide advice on statistical methods for evaluating alternative methods for NTP's toxicity and carcinogenicity testing. These include: 1) evaluating electrocardiogram data from a dog model for testing whether drugs prolong the QT wave in the heart beat which may ultimately lead to lethal arrhythmias, 2) providing advice about the analysis of high throughput data from cell-based assays of chemicals selected by the NTP, that were generated by the NIH Chemical Genomics Center, 3) providing advice about applying the up-and-down procedure to dermal toxicity testing, and 4) providing advice about how to combine in vitro test results to predict in vivo results.